Abstract：An improved unsymmetrical optimal pulse-width modulation (PWM) technique is proposed in this paper. The aim of this proposed technique is to decrease the relative calculation burden of a conventional unsymmetrical optimal PWM technique. The proposed optimal pulse pattern is synthesized by one well-known optimal pulse pattern of SHE (Selective Harmonic Elimination) technique and an unsymmetrical optimal pulse pattern. The transcendental mathematical equations are developed. Using the prior results of all complete solutions of SHE technique the solutions of the proposed equations are found by Newton iteration method. In particularly, a control range of a specific 5th harmonic is given by this proposed technique, and a three-dimensional diagram of switching angles about controlling of this harmonic according to its amplitude and phase angle is shown. Finally the modulation performance of the proposed technique for cascaded H-bridge inverters of line-voltage output is simulated and demonstrated by FFT analysis for its validity.Method
卜乐平, 张慧, 刘开培, 秦亮, 杨尚瑾, 凡念, 成威, 江政, 胡小乐. 非对称优化脉宽组合调制H-桥级联多电平逆变器的选择性谐波控制[J]. 电工技术学报, 2011, 26(11): 32-38.
Bu Leping, Zhang Hui, Liu Kaipei, Qin Liang, Yang Shangjin, Fan Nian, Cheng Wei, Jiang Zheng, Hu Xiaole. Study of a Synthesized Unsymmetrical Optimal PWM Technique of Selective Harmonic Controlling for Cascaded H-Bridge Multi-Level Inverters. Transactions of China Electrotechnical Society, 2011, 26(11): 32-38.
[1] Abu-Rub H, Holtz J, Rodriguez J, et al. Medium-voltage multilevel converters—state of the art, challenges, and requirements in industrial applications[J]. IEEE Transactions on Industrial Electronics, 2010, 57(8): 2581-2596. [2] Bowes S R, Holliday D. Optimal regular-sampled PWM inverter control techniques[J]. IEEE Transactions on Industrial Electronics, 2007, 54(4): 1547-1559. [3] Rodriguez J, Pontt J, Kouro S, et al. Direct torque control with imposed switching frequency in an 11-level cascaded inverter [J]. IEEE Transactions on Industrial Electronics, 2004, 51(4): 827-833. [4] Sundareswaran K, Jayant K, Shanavas T N. Inverter harmonic elimination through a colony of continuously exploring ants[J]. IEEE Transactions on Industrial Electronics, 2007, 54(5): 2558-2565. [5] Cho K M, Oh W S, Kim Y T, et al. A new switching strategy for pulse width modulation (PWM) power converters[J]. IEEE Transactions on Industrial Electronics, 2007, 54(1): 330-337. [6] Beig A R, Narayanan G, Ranganathan V T. Modified SVPWM algorithm for three level VSI with synchronized and symmetrical waveforms[J]. IEEE Transactions on Industrial Electronics, 2007, 54(1): 486-494. [7] Etxeberria-Otadui I, Viscarret U, Caballero M, et al, New optimized PWM VSC control structures and strategies under unbalanced voltage transients[J]. IEEE Transactions on Industrial Electronics, 2007, 54(5): 2902-2914. [8] Gonzalez S A, Garcia-Retegui R, Benedetti M. Harmonic computation technique suitable for active power filters[J]. IEEE Transactions on Industrial Electronics, 2007, 54(5): 2791-2796. [9] Patel H S, Hoft R G. Generalized techniques of harmonic elimination and voltage control in thyristor inverter: Part I—Harmonic elimination[J]. IEEE Transactions on Industry Application, 1973, IA-9(3): 310-317. [10] Zhang Hui, Liu KP, Braun M, Chan C C. Selective harmonic controlling for three-level high power active front end converter with low switching frequency[C]. Proceedings of the CES/IEE 5th International Power Electronics and Motion Control Conference, 2006. [11] Lascu C, Asiminoaei L, Boldea I. Frequency response
analysis of current controllers for selective harmonic compensation in active power filters[J]. IEEE Transactions on Industrial Electronics, 2009, 56(2): 337-347. [12] Du Zhong, Tolbert L M, Chiasson J N, et al. Reduced switching-frequency active harmonic elimination for multilevel converters[J]. IEEE Transactions on Industrial Electronics, 2008, 55(4): 1761-1770. [13] Rodriguez J, Lai J S, Peng F Z. Multilevel inverters: a survey of topologies, controls, and applications[J]. IEEE Transactions on Industrial Electronics, 2002, 49(4): 724-738.
2011, Vol. 26 
